Chemical Speciation of Chromium (III)and( VI) Using PhosphoniumCationImpregenated Polyurethane Fooms Prior to Their Spectrometric Determination
Fast and selective sorptions of Cr(VI) species from aqueous media onto tetraphenylphosphonium bromide (TPP+·Br–)
physically immobilized polyurethane foams (PUFs) sorbent were achieved. Based on the Scatchard model of binding
sites of the PUFs and Langmuir and Dubinin–Radushkevich (D–R) adsorption models of Cr(VI) retention onto TPP+·Br–
immobilized PUFs, a dual retention mechanism involving absorption related to “weak-base anion ion exchange” and an
added component for “surface adsorption” was proposed. Thus, the TPP+·Br– loaded PUFs were successfully packed in
column mode for preconcentration of trace and ultra trace concentrations of Cr(VI) as halochromates [CrO3C]–
aq from
aqueous HCl media. The retained [CrOCl3]–
aq species were recovered with NaOH (1.0 mol L–1) and analyzed by flame
atomic absorption spectrometry. Cr(III) species after oxidation to Cr(VI) with H2O2 in aqueous KOH (1.0 mol L–1) were
also retained and could be recovered by the proposed method. The limits of detection (LOD) and quantification (LOQ)
of Cr(VI) were 0.04 and 0.13 μg L–1, respectively. The chemical speciation of Cr(III, VI) species in various water
samples at trace and ultra trace levels were carried out by TPP+·Br– loaded PUFs packed column. The enhancement factor
and sensitivity factor of [CrO3C]–
aq sorption were 80.0 and 30.0, respectively.